1. Field of the Invention
The present invention relates to a plasma processing apparatus for generating a plasma by an electron cyclotron resonance (ECR) phenomenon and, more particularly, to a plasma processing apparatus suitably used as a semiconductor manufacturing apparatus such as an ECR etching apparatus or an ECR-CVD (ECR-Chemical Vapor Deposition) apparatus.
2. Description of the Related Art
Japanese Journal of Applied Physics Vol. 16, No. 11, Nov. 1977, pp. 1979-1984 (reference I), discloses a microwave plasma etching technique, and concludes as follows. In this technique, these fine patterns of 1 .mu.m size have been etched up to 1 .mu.m in depth without undercutting. This fine pattern etching has been difficult with conventional etching technique, and has been made possible by creating a plasma of high density at low pressure by microwave discharge. Etching by this technique is thought to be carried out by chemical reactions. Therefore, it is expected that the damage to the substrate is negligibly small and that the selectivity of etched materials is high. For instance, only Si is etched with a plasma of (CF.sub.4 +O.sub.2) mixture, leaving Al masks intact. The discharge area is shielded with a quartz tube to decrease the substrate contamination. Considering these advanced characteristics, this etching technique is thought to be suitable for semiconductor device processing. It is expected to make possible the fabrication of highly packing density integrated semiconductor devices.
Japanese Journal of Applied Physics Vol. 19, No. 5, May 1980, pp. 839-843 (reference II) discloses a technique on reduction of metal oxides by ECR plasma of hydrogen (a model study on discharge cleaning). In this technique, thick layers (.about.0.1 .mu.m) of oxides of Cu, Ni, Fe, Mo and Ti which have widely different binding energies (metal-oxygen) are reduced by an ECR plasma. Roughly speaking, the reduction rate decreases with an increase in binding energy. The reduction efficiency for Cu.sub.2 O is 0.8 initially and 0.4 on average. Concerning the other oxides, 10.sup.-3 &lt;.eta.&lt;10.sup.-2.
Japanese Journal of Applied Physics Vol. 21, No. 1, Jan. 1982, pp. 14-16 (reference III) discloses a technique on reactive ion beam etching using a broad beam ECR in source. A broad-beam ion source using microwave electron cyclotron resonance (ECR) discharge has been newly developed for reactive ion beam etching, ensuring high reliability in operation. Ion extration characteristics comparable to those of a Kaufman-type ion source are stably obtained for various reactive gases. The etching characteristics of various materials such as SiO.sub.2 and Al were investigated by introducing gases such as C.sub.4 F.sub.8 and SiCl.sub.4 into the ion source. Reactive ion beam etching using the broad-beam ECR ion source is very useful for high-accuracy pattern formation.
Japanese Journal of Applied Physics Vol. 22, No. 4, April 1983, pp. L210-L212 (reference IV) discloses a technique on low temperature chemical vapor deposition method utilizing an ECR plasma. The plasma deposition apparatus used in this technique can realize a deposition of dense and high quality thin films, such as Si.sub.3 N.sub.4 and SiO.sub.2, without the need for substrate heating. The deposition reactions are enhanced by using a microwave ECR plasma excitation at low gas pressures of 10.sup.-4 Torr, and a plasma extraction by a divergent magnetic field method, which bring about highly activated plasma and ion acceleration with moderate energies of 10 to 20 eV, respectively. The Si.sub.3 N.sub.4 and SiO.sub.2 films deposited are comparable to those prepared respectively by high temperature CVD and thermal oxidation, in evaluations such as by buffered HF solution etch rate measurement. The ECR plasma deposition method can be applied not only to silicon LSI, but also to compound semiconductor device fabrication processes.
Proc. Int'l Ion Engineering Congress - ISIAT'83 & IPAT'83, Kyoto (1983) (reference V) discloses a technique on a new reactive ion beam etching system for clean-surface-oriented dry etching technology. A new reactive ion beam etching system for investigating the elementary process of the clean-surface-oriented III-V compound etching is employed. As an example of good performance, GaAs etching with the smooth surface and the anisotropic, profile has been demonstrated. Preliminary work on "in-process" AES and SIMS has confirmed that the advanced studies about the etching kinetics can be expected by using the etching system shown here.